A matter of fact

This is a worrying time for those who believe government policies should be based on the best evidence. Pundits claim we’ve entered a postfactual era. Viral fake news stories spread alternative facts. On some issues, such as climate change and childhood vaccinations, many scientists worry their hard-won research findings have lost sway with politicians and the public, and feel their veracity is under attack. But just how should evidence shape policy? And why does it sometimes lose out? Those are just some of the questions tackled in this special section on evidence-based policymaking.